The present invention relates to wax dispersant and pour point improver additives for hydrocarbon lubricating oils derived from petroleum.
Two problems encountered with hydrocarbon lubricating oils are visible wax particles and the need for pour point improvement. Wax particles in lubricating oil can cause blockage of filters and delivery lines on equipment and engines, thus interfering with the flow of oil to moving parts. Wax particles in lubricating oils also cause the oil to look hazy. This is especially a problem in those oils such as automotive oils, turbine oils and the like which are desirably bright and clear in appearance at room temperature. These oils typically include fractions taken from paraffinic or naphthenic crude oils or crude oil blends from the Pennsylvania, Mid-Continent, Gulf Coast and West Coast regions.
Wax haze is generally not a problem in light oils such as household lubricants and naphthenic-type lubricating oils of less than about 200 SSU viscosity at 100.degree. F. Visible wax haze is primarily a problem in medium viscosity range oils such as naphthenic lube oils between 200 and 850 SSU viscosity at 100.degree. F. Wax haze or particles are considered to be present in more viscous oils; but discernment is difficult because these oils are dark and opaque.
The presence of wax haze is typically detected by simple observation with the human eye and at room temperatures--i.e., about 60.degree. to 80.degree. F. (15.degree. to 26.degree. C.). Instruments which measure light transmission may be employed to help determine the clarity of an oil. However, simple visual observation is normally relied upon.
The pour point of a lubricating oil can greatly affect the type of environments in which it can be used. Additionally, lowering the pour point of lubricating oils aids in pipeline transport and pumpability. The pour point of various viscosities of lubricating oils without additives ranges from +9.degree. C. for high viscosity oils to -18.degree. C. for low viscosity oils. Pour point depressants can typically lower pour points as much as 30.degree. C.
Using additives to reduce the pour point of various oils is well-known in the industry. Long chain fatty alkanol esters of copolymers of styrene and maleic anhydride and copolymers of alpha-olefins and maleic anhydride esterified with alcohols have been used as pour point depressants for fuels and lubricants. Other compounds which have been used as additives and dispersants are styrene-maleic anhydride copolymers reacted with aliphatic alcohols and tertiary amino alcohols, and ethylene vinyl acetate copolymers.
One important feature of an additive is that it be effective in small quantities. Another important feature is that the additive not produce unwanted by-products with its use in lubricating oil. An additive should also ideally perform more than one function so that fewer different additives have to be blended into the lubricating oil. Effectiveness in all viscosities and being liquid for ease of use are also desirable attributes in an additive. At the current time there is no additive available which acts both as a wax dispersant and a pour point improver much less one which meets the above criteria.